I've discovered a gotcha that happens when trying to use Cabal on Windows Vista. If you compile Setup.lhs to a binary (as I often do), with something like 'ghc --make Setup', and then try to run it, you'll get something like this: $ ./Setup configure Setup.exe: Permission denied This is due to a highly dubious security "feature" in Vista whereby it detects that you might be trying to run an installer-type program and refuses to execute the binary without elevated permissions. The idea is that ordinary users won't be confused when their installer fails partway through due to insufficient permissions. Unfortunately this works by matching on the name of the binary(!!!!), so names like "setup", "install" etc. are affected (there isn't a complete list, apparently). Other casualties are: * cabal-setup (compiles Setup.hs to setup.exe) * The GHC build system, which now uses Cabal * 'make install', which runs /usr/bin/install.exe More details in this MSDN thread: http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1021146&SiteID=1 and this Cygwin thread: http://www.cygwin.com/ml/cygwin/2006-12/msg00518.html Fortunately you can turn off the behaviour: Start->Run->secpol.msc, then Security Settings -> Local Policies -> Security Options ! UAC: Detect application installations and prompt for elevation. It appears you need to reboot for the change to take effect. The right workaround is to add a manifest to the binary asking for no security elevation, apparently this is quite easy. We'll need to get GHC to do this for every binary it generates in the future. For now, I'll put a note in the building guide and FAQ, and make a ticket for GHC 6.6.2 to do the manifest thing. Cheers, Simon